黑洞是冷的還是熱的？

Black holes (黑洞) are very cold, NOT hot.

The temperature of a black hole with mass the same as the mass of the Sun is only one ten-millionth of a degree above absolute zero (i.e. 10^-5 K). A black hole about the mass of the Moon has a temperature of 2.7 K

Since black holes are very massive objects, their densities are very very high. For black holes with the same mass as the Sun, the densities could reach 1.8 x10^16 g/cm^3.

References:

http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/971111e.html


http://en.wikipedia.org/wiki/Hawking_radiation

黑洞是冷的，可以(根據一些有關的公式)

氣體: P1V1/T1=P2V2/T2

不須理會p，只看v和t的關係。

其實這樣可以大約想得到就算不是氣體，只要密度大的話*(體積大密度就大)*，溫度

就自然大，反之亦然。

黑洞的密度大得可怕，因為它的半徑必須比*(史瓦西半徑)*小或相等。

史瓦西半徑:

R(s)=2GM/c^2

因此，它的體積必須很小，但質量要很大。

暫時所看到的

最冰冷的黑洞與絕對0度(大約-273.15度) 的相差只有 *1/(6x10^8)*度。
(則6億分之1度)

2014-07-23 17:04:45 補充：
致於硬:
可以說它比所有東西硬，因為硬和密度可以說是成正比。

2014-07-23 17:16:21 補充：
增加額外知識:
首先，黑洞是看不到的，因為史瓦西半徑的由來:
逃逸速度V=(2GM/r)^(1/2)
當逃逸速度是或大過光速時 V=c或>c
c=(2GM/r)^(1/2)
c^2=2GM/r
r=2GM/c^2
這就是史瓦西半徑的由來 則光不可能從黑洞中逃出。
則在黑洞中的光無法射入眼中，因此我們看不見。

另外，大家都對黑洞有一個誤解:
如果黑洞正在吸引一些物質時
你所看見的，不是這些物質超快地進入黑洞，反而是物質越接近黑洞，它的向心速度就越慢。則和常理相反，你

2014-07-23 17:26:12 補充：
首先要說我上面說的*它的向心速度就越慢*是指你所看的(它的向心速度)
地球吸引你的時候，你越接近地球，你的向心速度就越快，這是我們的常理，但現實往往和常理不同。
因為根據Lorentz's Transformation的神聖的公式:

t'=(t-ux/c^2)/平方根(1-u^2/c^2)
當一件物體的速度越接近光速時，時間過得越慢，到了光速時，時間就會停止，超光速時
*時間會倒流*(時光機的原理)^.^

因此有所謂的Absolute Horizon ，物體在此時 時間會停止!Stop!!

2014-07-26 16:09:18 補充：
簡單來說，熱脹冷x

不過霍金說黑洞不存在，科學家們對此有所懷疑。

2014-07-26 16:11:07 補充：
雖然宇宙是膨脹和冷的

2014-07-26 16:16:52 補充：
是喔 找到溫度的公式了*(只for黑洞)
(約化普朗克constant)c^3
T=---------------------------------------------------------------
8(pi)(k)(GM)

2014-07-26 16:18:56 補充：
希望你可以看得明白上面的公式 該這樣write
(約化普朗克constant)c^3
-------------------------------------------------=T
8(pi)(k)(GM)

It can be said that black holes are really just the evolutionary end point of massive stars. But somehow, this simple explanation makes them no less mysterious, and no easier to understand.

Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. If a star that massive or larger undergoes a supernova explosion, it may leave behind a fairly massive burned-out stellar remnant. With no outward forces to oppose gravitational forces, the remnant will collapse in on itself. The star eventually collapses to the point of zero volume and infinite density, creating what is known as a "singularity." Around the singularity is a region where the force of gravity is so strong that not even light can escape.
But contrary to popular myth, a black hole is not a cosmic vacuum cleaner. If our Sun was suddenly replaced with a black hole of the same mass, Earth's orbit around the Sun would be unchanged. Of course, Earth's temperature would change, and there would be no solar wind or solar magnetic storms affecting us. To be "sucked" into a black hole, one has to cross inside the Schwarzschild radius. At this radius, the escape speed is equal to the speed of light, and once light passes through, even it cannot escape.

The Schwarzschild radius can be calculated using the equation for escape speed:
vesc = (2GM/R)1/2
For photons, or objects with no mass, we can substitute c (the speed of light) for Vesc and find the Schwarzschild radius, R, to be

R = 2GM/c2

If the Sun was replaced with a black hole that had the same mass as the Sun, the Schwarzschild radius would be 3 km (compared to the Sun's radius of nearly 700,000 km). Hence the Earth would have to get very close to get sucked into a black hole at the center of our Solar System.
If we can't see them, how do we know they are there?

黑洞是熱的黑洞有幾硬,這個要科學家才解答得到!